Capillary fiber dialyzers are sold in large quantities by various companies for use as artificial kidneys for the dialysis of blood. Typically, these various commercial devices comprises a bundle of hollow fibers disposed in a generally rigid tubular housing, with the bundle and housing having relatively diametrically enlarged manifold members adjacent opposite housing ends. A sealing cap is then placed on each housing end, with the sealing cap defining a central port for the flow of blood from end to end of the housing, passing through the bores of the hollow fibers in the bundle.
Dialysis solution passes through the bundle of fibers in contact with the exterior surfaces of the individual fibers, entering the housing through a side port in one of the enlarged manifold members, and being withdrawn from another port in the side of the other enlarged manifold member. The ends of the bundle of hollow fibers are potted with a urethane material or the like, to stabilize the fibers and to secure them in a single mass, with the bores of the fibers being exposed to permit flow communication along their lengths. Frequently, an O-ring is provided between the end of the manifold member and the end closure member, to provide a hermetic seal.
In the conventional techniques of manufacturing hollow fiber dialyzers, the bundles of fragile fibers, upon assembly into dialyzers, exhibit a substantial number of instances of fiber breakage, occurrence of short fibers, and the like which results in leaking units which must be discarded or repaired. Often, some of the fibers misalign, and flare out into the enlarged manifold member, when they should remain in a discrete bundle during the potting process. This can result in a leakage situation, for even a single leaking fiber must result in the scrapping of the entire dialyzer unless it can be repaired.
The unit cost of dialyzers is increased by the need in many designs of a separate O-ring at its end for sealing. Also, the O-ring is conventionally compressed as the end closure member is applied to provide the seal. However, in the case of a vinyl O-ring or another material which is subject to cold flow upon storage, the dialyzer may lose its sealing capabilities provided by the O-ring because of the cold flow of the ring material in response to the compressive forces. The result of this is that the seal itself is weakened, and small amounts of blood may leak from the end closure of the dialyzer.
In accordance with this invention, an improved sealing system is provided in which a resilient sealing member is not placed under significant initial compression, so that significant cold flow does not take place upon storage. As a result of this, dialyzers in accordance with this invention may be stored indefinitely without a significant diminution of their good end sealing capabilities.
A capillary fiber diffusion device is provided herein which may be made with a significantly lower scrap rate, greatly reducing the unit cost of the dialyzer, which also has improved shelf life with respect to its end seals, and an intrinsically lower cost because a separate, preformed O-ring is not necessary in the designs proposed.